(1) Field of the Invention
The present invention relates to optical memory systems for optical data recording and reproduction, and more particularly to a pre-format configuration of optical disks and a method of data processing using the same.
(2) Description of the Related Art
In a prior art optical disk, as shown in FIG. 1, a transparent substrate 1 of PMMA (polymethyl methacrylate), PC (polycarbonate), etc. has grooves 2 which are formed concentrically or spirally and which define lands 3. 0n the lands 3, pre-pits 4 are provided, which correspond to track number data. Each land 3 forms a track, and it consists of a recording section 10 for writing data therein and a pre-format section 20 in which pre-pits 4 are formed in advance in correspondence to track number data.
When writing data on the optical disk, each land is tracked with a light spot to read out address data or the like represented by pre-pits 4 in the pre-format section 20 and then to write data in the recording section 10. When reading out data, each land 3 is tracked with the light spot 5 to read out address data or the like represented by pre-pits 4 in the pre-format section 20 and then read out data that has been written in the recording section 10.
There is great demand for increasing optical disk capacity, and there have been made extensive technical developments of wavelength reduction and track pitch reduction for recording and reproduction. In one technique of increasing the recording capacity of the optical disk, data is recorded in both lands and grooves. This technique is called a land/groove recording/reproducing technique. As described above, for recording and reading data, it is necessary to read out address data or the like that has been written in advance as pre-pits. To this end, it is necessary to form pre-pits in both the lands and the grooves.
Optical disks are roughly classified into two types depending on the position in which the pre-format section is formed. One of these types is a land type, in which pre-format sections are formed on lands of the optical disk. The other type is a groove type, in which pre-format sections are formed in grooves of the optical disk. In the pre-format section, the pre-pits are formed in a raised or recessed form.
As the process of forming the lands, grooves and pre-pits, an injecting molding process, a photopolymer (2P) process and a process of etching a glass or glass like substrate by using a mask disk, have been proposed. In the injecting molding process or the 2P process, a master disk is used. For preparing a master disk, an etching process using a mask disk is again essential. While it is necessary to form pre-pits in both the lands and the grooves for recording and reading data in the land/groove recording/reproducing technique, it is very difficult to form pre-pits in both the lands and the grooves.